The photostability of wool doped with photocatalytic titanium dioxide nanoparticles

Photoyellowing of wool is a serious problem for the wool industry. This study assessed the role of photocatalytic nanocrystalline titanium dioxide (P-25) as a potential antagonist or catalyst in the photoyellowing of wool. Untreated, bleached and bleached and fluorescent-whitened wool slivers were processed into fine wool powders for the purpose of even and intimate mixing with the TiO₂ nanoparticles in the solid state. Pure wool and wool/TiO₂ mixtures were then compressed into solid discs for a photoyellowing study under simulated sunlight and under UVB and UVC radiations. Yellowness and photo-induced chemiluminescence (PICL) measurements showed that nanocrystalline TiO₂ could effectively reduce the rate of photoyellowing by inhibiting free radical generation in doped wool, and that a higher concentration of TiO₂ contributed to a lower rate of photooxidation and reduced photoyellowing. Hence nanocrystalline TiO₂ acts primarily as a UV absorber on wool in dry conditions and not as a photocatalyst.